Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$50.81	4.558%	$53.1259	$53.13	$53.15	$53.10
Purchase #2	$238.45	11.322%	$265.4473	$265.45	$265.45	$265.40
Purchase #3	$206.78	7.290%	$221.8543	$221.85	$221.85	$221.90
Purchase #4	$165.87	4.142%	$172.7403	$172.74	$172.75	$172.70
Purchase #5	$185.37	13.487%	$210.3709	$210.37	$210.35	$210.40
Purchase #6	$173.98	5.486%	$183.5245	$183.52	$183.50	$183.50
Purchase #7	$245.81	13.478%	$278.9403	$278.94	$278.95	$278.90
7 purchase totals =	$1,267.07		$1,386.0035	$1,386.00	$1,386.00	$1,385.90